Silicon anodes with water-soluble maleic anhydride-, and/or maleic acid-containing polymers/copolymers, derivatives, and/or combinations (with or without additives) as binders

ABSTRACT

Systems and methods for batteries comprising a cathode, an electrolyte, and an anode, wherein the anode is a Si-dominant anode that utilizes water-soluble maleic anhydride- and/or maleic acid-containing polymers/co-polymers, derivatives, and/or combinations (with or without additives) as binders.

TECHNICAL FIELD

Aspects of the present disclosure relate to energy generation andstorage. More specifically, certain embodiments of the disclosure relateto a method and system for using water-soluble polymers as binders forsilicon anodes in Li-ion battery electrodes.

BACKGROUND

Conventional approaches for battery electrodes may cause electrodecoating layers to lose contact with the electrode and/or may requiretoxic and/or difficult manufacturing.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present disclosureas set forth in the remainder of the present application with referenceto the drawings.

BRIEF SUMMARY

A system and/or method for using water-soluble polymers and/orco-polymers such as those comprising maleic anhydride and/or maleic acidas binders for silicon anodes in Li-ion battery electrodes,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentdisclosure, as well as details of an illustrated embodiment thereof,will be more fully understood from the following description anddrawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A and 1B are diagrams of a battery, in accordance with an exampleembodiment of the disclosure. FIG. 1A is a simplified example batteryand FIG. 1B shows realistic battery structures.

FIG. 2 is a flow diagram of a direct coating process for fabricating acell with a silicon-dominant electrode, in accordance with an exampleembodiment of the disclosure.

FIG. 3 is a photo of 20 wt % Poly(methyl vinyl ether-alt-maleicanhydride) (PMVMA) aqueous solution, in accordance with an exampleembodiment of the disclosure.

FIG. 4 is a photo of a direct coated Si anode with 20 wt % Poly(methylvinyl ether-alt-maleic anhydride) (PMVMA) aqueous solution as binder, inaccordance with an example embodiment of the disclosure.

FIG. 5 shows TGA curves of Poly(methyl vinyl ether-alt-maleic anhydride)(PMVMA) under Argon, in accordance with an example embodiment of thedisclosure.

FIG. 6 shows an adhesion test for an anode pyrolyzed at 700° C. withPMVMA as binder, in accordance with an example embodiment of thedisclosure.

FIG. 7 is a photo showing the result of a winding test for a Si anodepyrolyzed at 700° C. with PMVMA as binder, in accordance with an exampleembodiment of the disclosure.

FIGS. 8A and 8B demonstrate Capacity retention (FIG. 8A) and Normalizedcapacity retention (FIG. 8B) of: (dotted line) standard Si anode//NCAcathode full cells—Control; and (solid line) as-fabricated Si anode//NCAcathode full cells using 20 wt % PMVMA aqueous solution followed byannealing at 550° C., in accordance with an example embodiment of thedisclosure.

FIGS. 9A and 9B demonstrate Capacity retention (FIG. 9A) and Normalizedcapacity retention (FIG. 9B) of: (dotted line) standard Si anode//NCAcathode full cells—Control; and (solid line) as-fabricated Si anode//NCAcathode full cells using 20 wt % PMVMA aqueous solution with PEI, inaccordance with an example embodiment of the disclosure.

FIGS. 10A and 10B demonstrate Capacity retention (FIG. 9A) andNormalized capacity retention (FIG. 9B) of: (dotted line) standard Sianode//NCA cathode full cells—Control; and (solid line) as-fabricated Sianode//NCA cathode full cells using 20 wt % PMVMA aqueous solutionfollowed by annealing at 700° C., in accordance with an exampleembodiment of the disclosure.

FIGS. 11A and 11B demonstrate Capacity retention (FIG. 11A) andNormalized capacity retention (FIG. 11B) of: (dotted line) standard Sianode//NCA cathode full cells—Control; and (solid line) as-fabricated Sianode//NCA cathode full cells using 20 wt % PMVMA aqueous solution withβ-Cyclodextrin (β-CD), in accordance with an example embodiment of thedisclosure.

FIGS. 12A and 12B demonstrate Capacity retention (FIG. 12A) andNormalized capacity retention (FIG. 12B) of: (dotted line) standard Sianode//NCA cathode full cells—Control; and (solid line) as-fabricated Sianode//NCA cathode full cells using 20 wt % PMVMA aqueous solution withTannic Acid, in accordance with an example embodiment of the disclosure.

FIGS. 13A and 13B demonstrate Capacity retention (FIG. 13A) andNormalized capacity retention (FIG. 13B) of: (dotted line) standard Sianode//NCA cathode full cells—Control; and (solid line) as-fabricated Sianode//NCA cathode full cells using 20 wt % PMVMA aqueous solution withTannic Acid and 1 wt % Super P followed by annealing at 700° C., inaccordance with an example embodiment of the disclosure.

FIGS. 14A and 14B demonstrate Capacity retention (FIG. 14A) andNormalized capacity retention (FIG. 14B) of: (dotted line) standard Sianode//NCA cathode full cells—Control; and (solid line) as-fabricated Sianode//NCA cathode full cells using 20 wt % PMVMA aqueous solution withTannic Acid and 2 wt % Super P followed by annealing at 550° C., inaccordance with an example embodiment of the disclosure.

FIGS. 15A and 15B demonstrate Capacity retention (FIG. 15A) andNormalized capacity retention (FIG. 15B) of: (dotted line) standard Sianode//NCA cathode full cells—Control; and (solid line) as-fabricated Sianode//NCA cathode full cells using 20 wt % PMVMA aqueous solution withTannic Acid and 5 wt % Super P followed by annealing at 550° C., inaccordance with an example embodiment of the disclosure.

DETAILED DESCRIPTION

FIGS. 1A and 1B are diagrams of a battery, in accordance with an exampleembodiment of the disclosure. Referring to FIG. 1A, there is shown abattery 100 comprising a separator 103 sandwiched between an anode 101and a cathode 105, with current collectors 107A and 107B. There is alsoshown a load 109 coupled to the battery 100 illustrating instances whenthe battery 100 is in discharge mode. In this disclosure, the term“battery” may be used to indicate a single electrochemical cell, aplurality of electrochemical cells formed into a module, and/or aplurality of modules formed into a pack. Furthermore, the cell shown inFIG. 1A is a very simplified example merely to show the principle ofoperation of a lithium ion cell. Examples of realistic batterystructures are shown in FIG. 1B, where stacks of electrodes andseparators are utilized, with electrode coatings typically on both sidesof the current collectors. The stacks may be formed into differentshapes, such as a coin cell, cylindrical cell, or prismatic cell, forexample.

The development of portable electronic devices and electrification oftransportation drive the need for high performance electrochemicalenergy storage. Small-scale (<100 Wh) to large-scale (>10 KWh) devicesprimarily use lithium-ion (Li-ion) batteries over other rechargeablebattery chemistries due to their high-performance.

The anode 101 and cathode 105, along with the current collectors 107Aand 107B, may comprise the electrodes, which may comprise plates orfilms within, or containing, an electrolyte material, where the platesmay provide a physical barrier for containing the electrolyte as well asa conductive contact to external structures. In other embodiments, theanode/cathode plates are immersed in electrolyte while an outer casingprovides electrolyte containment. The anode 101 and cathode areelectrically coupled to the current collectors 107A and 107B, whichcomprise metal or other conductive material for providing electricalcontact to the electrodes as well as physical support for the activematerial in forming electrodes.

The configuration shown in FIG. 1A illustrates the battery 100 indischarge mode, whereas in a charging configuration, the load 107 may bereplaced with a charger to reverse the process. In one class ofbatteries, the separator 103 is generally a film material, made of anelectrically insulating polymer, for example, that prevents electronsfrom flowing from anode 101 to cathode 105, or vice versa, while beingporous enough to allow ions to pass through the separator 103.Typically, the separator 103, cathode 105, and anode 101 materials areindividually formed into sheets, films, or active material coated foils.Sheets of the cathode, separator and anode are subsequently stacked orrolled with the separator 103 separating the cathode 105 and anode 101to form the battery 100. In some embodiments, the separator 103 is asheet and generally utilizes winding methods and stacking in itsmanufacture. In these methods, the anodes, cathodes, and currentcollectors (e.g., electrodes) may comprise films.

In an example scenario, the battery 100 may comprise a solid, liquid, orgel electrolyte. The separator 103 preferably does not dissolve intypical battery electrolytes such as compositions that may comprise:Ethylene Carbonate (EC), Fluoroethylene Carbonate (FEC),Di-fluoroethylene carbonate (DiFEC), Propylene Carbonate (PC), Vinylenecarbonate (VC), Trifluoropropylene carbonate (TFPC), Dimethyl Carbonate(DMC), Ethyl Methyl Carbonate (EMC), Diethyl Carbonate (DEC), etc. withdissolved LiBF₄, LiAsF₆, LiPF₆, Lithium bis(oxalato)borate (LiB(C₂O₄)₂;LiBOB), Lithium difluoro(oxalato)borate (LiBF₂(C₂O₄); LiDFOB), Lithium2-trifluoromethyl-4,5-dicyanoimidazole (C₆F₃LiN₄; LiTDI), Lithiumbis(trifluoromethanesulfonyl)imide (LiC₂F₆NO₄S₂; LiTFSI), Lithiumbis(fluorosulfonyl)imide (F₂LiNO₄S₂, LiFSI), LiPO₂F₂, LiSiF₆, LiClO₄,Lithium triflate (LiCF₃SO₃), Lithium tetrafluorooxalato phosphate(LTFOP), Lithium pentafluoroethyltrifluoroborate (LiFAB), Lithiumbis(2-fluoromalonato)borate (LiBFMB), Lithium 4-pyridyl trimethyl borate(LPTB), Lithium 2-fluorophenol trimethyl borate (LFPTB), Lithiumcatechol dimethyl borate (LiCDMB), etc. The separator 103 may be wet orsoaked with a liquid or gel electrolyte. In addition, in an exampleembodiment, the separator 103 does not melt below about 100 to 120° C.,and exhibits sufficient mechanical properties for battery applications.A battery, in operation, can experience expansion and contraction of theanode and/or the cathode. In an example embodiment, the separator 103can expand and contract by at least about 5 to 10% without failing, andmay also be flexible.

The separator 103 may be sufficiently porous so that ions can passthrough the separator once wet with, for example, a liquid or gelelectrolyte. Alternatively (or additionally), the separator may absorbthe electrolyte through a gelling or other process even withoutsignificant porosity. The porosity of the separator 103 is alsogenerally not too porous to allow the anode 101 and cathode 105 totransfer electrons through the separator 103.

The anode 101 and cathode 105 comprise electrodes for the battery 100,providing electrical connections to the device for transfer ofelectrical charge in charge and discharge states. The anode 101 maycomprise silicon, carbon, or combinations of these materials, forexample. Typical anode electrodes comprise a carbon material thatincludes a current collector such as a copper sheet. Carbon is oftenused because it has excellent electrochemical properties and is alsoelectrically conductive. Anode electrodes currently used in rechargeablelithium-ion cells typically have a specific capacity of approximately200 milliamp hours per gram. Graphite, the active material used in mostlithium ion battery anodes, has a theoretical energy density of 372milliamp hours per gram (mAh/g). In comparison, silicon has a hightheoretical capacity of 4200 mAh/g. In order to increase volumetric andgravimetric energy density of lithium-ion batteries, silicon may be usedas the active material for the cathode or anode. Silicon anodes may beformed from silicon composites, with more than 50% silicon, for example.

In an example scenario, the anode 101 and cathode 105 store the ion usedfor separation of charge, such as lithium. In this example, theelectrolyte carries positively charged lithium ions from the anode 101to the cathode 105 in discharge mode, as shown in FIG. 1 for example,and vice versa through the separator 105 in charge mode. The movement ofthe lithium ions creates free electrons in the anode 101 which creates acharge at the positive current collector 107B. The electrical currentthen flows from the current collector through the load 109 to thenegative current collector 107A. The separator 103 blocks the flow ofelectrons inside the battery 100, allows the flow of lithium ions, andprevents direct contact between the electrodes.

While the battery 100 is discharging and providing an electric current,the anode 101 releases lithium ions to the cathode 105 via the separator103, generating a flow of electrons from one side to the other via thecoupled load 109. When the battery is being charged, the oppositehappens where lithium ions are released by the cathode 105 and receivedby the anode 101.

The materials selected for the anode 101 and cathode 105 are importantfor the reliability and energy density possible for the battery 100. Theenergy, power, cost, and safety of current Li-ion batteries need to beimproved in order to, for example, compete with internal combustionengine (ICE) technology and allow for the widespread adoption ofelectric vehicles (EVs). High energy density, high power density, andimproved safety of lithium-ion batteries are achieved with thedevelopment of high-capacity and high-voltage cathodes, high-capacityanodes and functionally non-flammable electrolytes with high voltagestability and interfacial compatibility with electrodes. In addition,materials with low toxicity are beneficial as battery materials toreduce process cost and promote consumer safety.

FIG. 2 is a flow diagram of a direct coating process for fabricating acell with a silicon-dominant electrode, in accordance with an exampleembodiment of the disclosure. This process comprises physically mixingthe electrode coating layer with a polymer (resin) binder aqueoussolution, and coating it directly on a current collector. This processis different from traditional processes of forming the electrode coatinglayer on a substrate and then laminating it on a current collector. Thisstrategy may also be adopted by other anode-based cells, such asgraphite, conversion type anodes, such as transition metal oxides,transition metal phosphides, and other alloy type anodes, such as Sn,Sb, Al, P, etc.

In step 201, the raw electrode coating layer may be mixed to form aslurry with stable viscosities. Changing the nature of and/or themolecular weight of the polymer binder enables the adjustment of theviscosity of the polymer and homogenization of the slurry. Thefabricated anode shows good adhesion to copper and enhanced cohesion,and flexibility.

The particle size and mixing times may be varied to configure theelectrode coating layer density and/or roughness. Furthermore, cathodeelectrode coating layers may be mixed in step 201, where the electrodecoating layer may comprise lithium cobalt oxide (LCO), lithium ironphosphate, lithium nickel cobalt manganese oxide (NMC), Ni-rich lithiumnickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO),lithium nickel manganese spinel, Lithium Iron phosphate (LFP), Li-richlayer-layer cathodes, LiNi_(0.5)Mn_(1.5)O₄ (LNMO) or similar materialsor combinations thereof.

In step 203, the as-prepared slurry may be coated on a copper foil, 15μm thick in this example, and in step 205 may be dried at 130° C. in aconvection oven to dry the coating and form the green anode. Similarly,cathode electrode coating layers may be coated on a foil material, suchas aluminum, for example.

An optional calendering process may be utilized in step 207 where aseries of hard pressure rollers may be used to finish the film/substrateinto a smoother and denser sheet of material. The calendaringtemperature range may be about 60° C.-180° C. Cells can be directlypunched and fabricated after calendaring.

In some embodiments, the electrode coating layer may be pyrolyzed as instep 209 by heating to 500-800° C., 700° C. in this example, in an inertatmosphere such that carbon precursors are partially or completelyconverted into conductive carbon. The pyrolysis step may result in ananode electrode coating layer having silicon content greater than orequal to 50% by weight, where the anode has been subjected to heating ator above 400 degrees Celsius.

Pyrolysis can be done either in roll form or after punching in step 211.If done in roll form, the punching is done after the pyrolysis process.In instances where the current collector foil is notpre-punched/pre-perforated, the formed electrode may be perforated witha punching roller, for example. The punched electrodes may then besandwiched with a separator and electrolyte to form a cell. In step 213,the cell may be subjected to a formation process, comprising initialcharge and discharge steps to lithiate the anode, with some residuallithium remaining, and the cell capacity may be assessed.

As the demands for both zero-emission electric vehicles and grid-basedenergy storage systems increase, lower costs and improvements in energydensity, power density, and safety of lithium (Li)-ion batteries arehighly desirable. Enabling the high energy density and safety of Li-ionbatteries requires the development of high capacity, and high-voltagecathodes and high-capacity anodes.

As discussed above, a lithium-ion battery typically includes a separatorand/or electrolyte between an anode and a cathode. In one class ofbatteries, the separator, cathode and anode materials are individuallyformed into sheets or films. Sheets of the cathode, separator and anodeare subsequently stacked or rolled with the separator separating thecathode and anode (e.g., electrodes) to form the battery. Typicalelectrodes include electro-chemically active material layers onelectrically conductive metals (e.g., aluminum and copper). Films can berolled or cut into pieces, which are then layered into stacks. Thestacks are of alternating electro-chemically active materials with theseparator between them.

Silicon (Si)-based electrodes for Li-ion batteries are attractive forseveral reasons including: (i) high theoretical capacity of about 3579mAh/g at room temperature, which is about 10 times that of conventionalgraphite anodes; (ii) relatively low lithiation/delithiation potentialof ˜0.4V versus Li/Li⁺; (iii) silicon is abundant and the price is low,and (iv) environmental impact of Si is low. However, the practical useof Si anodes in Li-ion batteries may be hindered by its poor performanceresulting from the low intrinsic electrical conductivity and the hugevolume expansion (up to 300%). The concomitant local strain duringexpansion pulverizes Si at the particle level and deteriorates thephysical/electrical contact with both the charge carrier and currentcollector at the electrode level. In the meantime, the severecompression/tensile stress, upon the expansion/contraction of Li—Sialloy, ruptures the SEI layer formed at the electrode surface.Subsequently, this may cause cracks, allowing exposure to theelectrolyte. As a result, the cyclability, rate capability, andCoulombic efficiency (CE) of the batteries deteriorate upon sustainedcycling.

Thus, for anodes, silicon-based materials can provide significantimprovement in energy density but the large volumetric expansion (>300%)during the Li alloying/dealloying processes can lead to disintegrationof the active material and the loss of electrical conduction paths,thereby reducing the cycling life of the battery. In addition, anunstable solid electrolyte interphase (SEI) layer can develop on thesurface of the cycled anodes, and leads to an endless exposure of Siparticle surfaces to the liquid electrolyte. This results in anirreversible capacity loss at each cycle due to the reduction at the lowpotential where the liquid electrolyte reacts with the exposed surfaceof the Si anode. In addition, oxidative instability of the conventionalnon-aqueous electrolyte takes place at voltages beyond 4.5 V, which canlead to accelerated decay of cycling performance. Si/carbon compositesmay be used because carbon undergoes only small volume change during theLi insertion and dimensional stability can be preserved. However,because of the generally inferior cycle life of Si compared to graphite,only small amounts of Si or Si alloy is used in conventional anodematerials. Previous studies focused on Si anodes have only shown lowloading of active materials; thus they are very difficult to scale up orcommercialize.

Binders are important in Li ion batteries as they promote adhesionbetween electrodes (e.g. electrode films) and collectors and can have aneffect on the coverage of active materials. Binders hold active materialparticles together, acting as a connector between electrode specieswhile adhering them to the collectors. Binders allow for greaterstability and conduction in a battery. The use of binders in electrodesmay increase life span and/or energy density. In a Si anode, the bindermay stabilize the silicon particles.

Polyvinylidene fluoride (PVDF) is a highly non-reactive thermoplasticfluoropolymer produced by the polymerization of vinylidene difluorideand is a commonly-used binder in conventional Li-ion batteries becauseof its acceptable adhesion and wide electrochemical window. However,PVDF binder can only attach to Si particles via weak van der Waals forcefor its non-functionalized linear chain structure. Thus PVDF binderprovides poor accommodation of large volume changes of Si. In addition,the toxic organic solvent N-methyl-2-pyrrolidone (NMP) has to be usedwhen used PVDF as a binder.

In addition to the binder, the performance of Si anode is also closelyrelated with the fabrication process of the electrode since itdetermines the distribution, connection, and macrostructure of theelectrode layer. Optimization of the fabrication process leads to thecheaper production of electrodes with improved properties like capacity,cyclability, safety, cost, etc. There is a trade-off in the electrodedesign for high energy and power density. The electronic conductivityresulting from a carbon conductive additive can be brought down by thepresence of a nonconductive binder. The existence of a carbon conductiveadditive also weakens the binding network of polymer binders. In thetraditional high conductive graphite anode, the negative effect isacceptable due to the limited added amount. However, in the era of thehigh capacity Si anode, especially, Si-dominant anodes (≥70% Si) withlarge volume expansion and low electronic conductivity, relatively highamounts of carbon conductive material are essential.

In the present disclosure, the use of water-soluble maleic anhydride-and/or maleic acid-containing polymers/co-polymers, derivatives, and/orcombinations as binders in electrode coating layers for Si anodes isdescribed. These polymers (resins) have unique chemical structures andfunctional groups which may bring the following benefits: (i) increasedbinding; (ii) increased conductivity; (iii) decreased cost; and/or and(iv) increased environmental safety (environmentally benign). Thebinders may include water-soluble polymers such as maleic anhydride-,poly maleic acid-containing polymers, derivatives, or combinations withother crosslinkers and/or additives. These polymers (resins) areamphoteric, containing —COOH, anhydride, and/or other functional groups,which makes them suitable for bonding Si powders (containing —OHgroups). In addition, these water-soluble polymers (resins) can helppromote the dispersion of Si active materials and conductive additives,provide good connection among them, and provide strong adhesion withmetal current collectors. They are also commercially available, cheap,environmentally friendly and water-soluble, which can avoid theutilization of toxic solvents, such as NMP.

In addition, maleic anhydride- and/or maleic acid-containingpolymers/co-polymers, derivatives, and/or combinations when used asbinders in electrode coating layers for anodes can aid in the creationof spaces formed between Si particles during the heat treatment of theelectrode, allowing for Si expansion during cycling and facilitating thepenetration of the liquid electrolyte into active materials, which ishelpful in promoting Li-ion transport. The present application describesfurther carbonizing Si anodes containing water-soluble maleic anhydride-and/or maleic acid-containing polymer (resin) binders to enhance theelectrode conductivity. Carbonizing (partially or fully) the resin bypyrolysis (annealing) may result in spaces forming among Si particles asdiscussed above and as a result, a Si anode with a partially carbonizedbinder in accordance with the disclosure shows better electrochemicalperformance than a traditionally directly coated Si anode withoutannealing processes at high Si content and high current density.

Composite materials can be used as an anode in most conventional Li-ionbatteries; they may also be used as the cathode in some electrochemicalcouples with additional additives. Composite materials described hereincan be, for example, silicon composite materials, carbon compositematerials, and/or silicon-carbon composite materials. In certainembodiments, the composite materials may be self-supported structures.In further embodiments, the composite materials may be self-supportedmonolithic structures.

Anode electrodes currently used in rechargeable lithium-ion cellstypically have a specific capacity of approximately 200 milliamp hoursper gram (including the metal foil current collector, conductiveadditives, and binder material). Graphite, the active material used inmost lithium ion battery anodes, has a theoretical energy density of 372milliamp hours per gram (mAh/g). In comparison, silicon has a hightheoretical capacity of 4200 mAh/g. In order to increase volumetric andgravimetric energy density of lithium-ion batteries, silicon may be usedas the active material for the cathode or anode. Several types ofsilicon materials, e.g., silicon nanopowders, silicon nanofibers, poroussilicon, and ball-milled silicon, have also been reported as viablecandidates as active materials for the negative or positive electrodes.In some embodiments, a high capacity Si anode is used that is more than70% Si.

Small particle sizes (for example, sizes in the nanometer range)generally can increase cycle life performance. They also can displayvery high initial irreversible capacity. However, small particle sizesalso can result in very low volumetric energy density (for example, forthe overall cell stack) due to the difficulty of packing the activematerial. Larger particle sizes, (for example, sizes in the micronrange) generally can result in higher density anode material. However,the expansion of the silicon active material can result in poor cyclelife due to particle cracking. For example, silicon can swell in excessof 300% upon lithium insertion. Because of this expansion, anodesincluding silicon need to allow expansion while maintaining electricalcontact between the silicon particles. As discussed above, the use ofwater-soluble maleic anhydride- and/or maleic acid-containing polymersas binders as disclosed for Si anodes allows for free spaces to becreated among Si particles during the pyrolysis process. These freespaces allow for the necessary expansion, creating the extra volumerequired for Si expansion during cycling.

In some embodiments, a largest dimension of the silicon particles can beless than about 40 μm, less than about 1 μm, between about 10 nm andabout 40 μm, between about 10 nm and about 1 μm, less than about 500 nm,less than about 100 nm, and about 100 nm. All, substantially all, or atleast some of the silicon particles may comprise the largest dimensiondescribed above. For example, an average or median largest dimension ofthe silicon particles can be less than about 40 μm, less than about 1μm, between about 10 nm and about 40 μm, between about 10 nm and about 1μm, less than about 500 nm, less than about 100 nm, and about 100 nm.The amount of silicon in the composite material can be greater than zeropercent by weight of the mixture and composite material. In certainembodiments, the mixture comprises an amount of silicon, the amountbeing within a range of from about 0% to about 90% by weight, includingfrom about 30% to about 80% by weight of the mixture. The amount ofsilicon in the composite material can be within a range of from about 0%to about 35% by weight, including from about 0% to about 25% by weight,from about 10% to about 35% by weight, and about 20% by weight. Infurther certain embodiments, the amount of silicon in the mixture is atleast about 30% by weight. Additional embodiments of the amount ofsilicon in the composite material include more than about 50% by weight,between about 30% and about 80% by weight, between about 50% and about70% by weight, and between about 60% and about 80% by weight.Furthermore, the silicon particles may or may not be pure silicon. Forexample, the silicon particles may be substantially silicon or may be asilicon alloy. In one embodiment, the silicon alloy includes silicon asthe primary constituent along with one or more other elements.

As described herein, micron-sized silicon particles can provide goodvolumetric and gravimetric energy density combined with good cycle life.In certain embodiments, to obtain the benefits of both micron-sizedsilicon particles (e.g., high energy density) and nanometer-sizedsilicon particles (e.g., good cycle behavior), silicon particles canhave an average particle size in the micron range and a surfaceincluding nanometer-sized features. In some embodiments, the siliconparticles have an average particle size (e.g., average diameter oraverage largest dimension) between about 0.1 μm and about 30 μm orbetween about 0.1 μm and all values up to about 30 μm. For example, thesilicon particles can have an average particle size between about 0.5 μmand about 25 μm, between about 0.5 μm and about 20 μm, between about 0.5μm and about 15 μm, between about 0.5 μm and about 10 μm, between about0.5 μm and about 5 μm, between about 0.5 μm and about 2 μm, betweenabout 1 μm and about 20 μm, between about 1 μm and about 15 μm, betweenabout 1 μm and about 10 μm, between about 5 μm and about 20 μm, etc.Thus, the average particle size can be any value between about 0.1 μmand about 30 μm, e.g., 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm,25 μm, and 30 μm.

Cathode electrodes described herein may include metal oxide cathodeactive materials, such as one or more of: Lithium Cobalt Oxide (LiCoO₂)(LCO), Ni-rich oxides, high voltage cathode materials, lithium-richoxides, nickel-rich layered oxides, lithium rich layered oxides,high-voltage spinel oxides, and high-voltage polyanionic compounds.Ni-rich oxides and/or high voltage cathode materials may include nickelcobalt aluminum oxide (NCA), nickel cobalt manganese oxide (NCM). Oneexample of a NCM material includes LiNi_(0.6)Co_(0.2)Mn_(0.2)O₂(NCM-622). Lithium rich oxides may includexLi₂Mn₃O₂.(1−x)LiNi_(a)Co_(b)Mn_(c)O₂. Nickel-rich layered oxides mayinclude LiNi_(1+x)Mi_(1−x)O_(z) (where M=Co, Mn or Al). Lithium richlayered oxides may include LiNi_(1+x)M_(1−x)O₂ (where M=Co, Mn or Ni).High-voltage spinel oxides may include LiNi_(0.5)Mn_(1.5)O₄.High-voltage polyanionic compounds may include phosphates, sulfates,silicates, etc. In accordance with the disclosure, “active material” maycomprise the active material alone, or may encompass an entire electrodecoating layer, which includes the active material and other components.

The present application describes using water-soluble maleic anhydride-and/or poly maleic acid-containing polymers, including polymerderivatives, and/or combinations with other crosslinkers or additives aswater-soluble functional binders in electrode coating layers for Sianode-based Li-ion full cells with subsequent pyrolysis processes.Polymers of varying molecular weights may be used. In some embodiments,the polymers may be co-polymers; in other embodiments the polymers maybe alternating co-polymers. In some embodiments, the polymers may bealkali salts, such as sodium (Na) salts or lithium (Li) salts. In someembodiments, the polymers may be grafted polymers. In some embodiments,the polymers are linked with a crosslinker (crosslinking compound) thathas two or more reactive groups thereon. In other embodiments, thepolymers may include more than one of the above types combined in onepolymer compound.

Polymers are created from monomers and the molecular weight (MW) of apolymer is based on the identity of the monomer and the number ofmonomers present in the polymer molecule. Polymer molecular weights areusually given as averages and may fall in a distribution. The MWdistribution determines the properties of the polymer. In themeasurement of the average MW, the two most common ways to measure areMn, number averaged MW, and Mw, weight averaged MW (midpoint of thedistribution in terms of the number of molecules). Polydispersity of apolymer (Mw:Mn ratio) describes the distribution width. Other ways tocalculate MW include viscosity average molecular weight (Mv), and higheraverage molecular weight (Mz, Mz+1). The choice of method for polymermolecular weight determination depends on factors such as cost,experimental conditions and requirements.

In some embodiments, the polymer binder-containing Si anodes are furtherpyrolyzed/carbonized to enhance the electrode conductivity of theas-fabricated Si anodes. Thus presently described functional binders canenhance the adhesion and/or conductivity of a Si anode and promote thedispersion of Si active materials and conductive additive(s), whileproviding good connections and strong adhesion to the Cu currentcollector.

In some embodiments, crosslinkers may be used to crosslink the polymers,providing changes to the functionality and molecular weights and thusthe properties of the polymer binder. Furthermore, in other embodiments,additives can be used along with the water-soluble maleic anhydride-and/or maleic acid-containing polymers. Additives include, but are notlimited to, one or more conductive additives and/or functional compoundadditives such as polymers, water-soluble polymers and/or othercompounds as described above. Concentrations of additives may be about 1wt % to 100 wt % relative to the polymers as binders. In someembodiments, the concentration may be 1 wt % to 50 wt % relative to thepolymer binders; in other embodiments, the concentration may be 10 wt %to 40 wt % relative to the polymer binders.

Water-soluble maleic anhydride- and/or maleic acid-containing polymershave good solubility in water with adjustable viscosity due to theirunique functional polar groups. The polymers can have stronginteractions with both Si powders and Cu foil, so slurries madeincluding the binders have good quality and also have excellent adhesionwith Cu foil after coating. This can contribute to the overall cycleperformance improvement. In addition, these polymers have improved charyield after pyrolysis/annealing at high temperature so the prepared Sianodes can also be pyrolyzed in a temperature range that will not have anegative impact on the flexibility and other mechanical properties ofthe electrodes, but can help increase conductivity. Without being boundto the theory or mode of operation, it is believed that these maleicanhydride- and/or maleic acid-containing polymer binders allow for freespaces to be created among Si particles during the pyrolysis/annealingprocess. These free spaces can help accommodate the extra volumerequired for Si expansion during cycling and can facilitate thepenetration of the liquid electrolyte into active materials, which ishelpful in promoting Li-ion transport.

In accordance with the disclosure, maleic anhydride- and/or maleicacid-containing polymers, derivatives, and/or combinations when used asbinders for anodes may have one or more of the following advantageousproperties: (i) high solubility in water; (ii) increased safety; (iii)functional groups which can improve the interactions with the metalfoil; (iv) easily crosslinked; (v) high carbon yield upon pyrolysis;(vi) adjustable viscosity; (vii) ease in processing; (ix) low cost and(x) environmentally friendly.

Maleic anhydride- and/or maleic acid-containing polymers/co-polymershave good solubility in water due to their polar nature; maleicacid-containing polymers are easy to dissolve into water directly andmaleic anhydride-containing polymers hydrolyze and form acidiccomponents, which are soluble. Thus these polymers are hydrophilic. Insome embodiments, these polymers contain functional groups which canincrease interactions resulting in good adhesion to metal foil-basedcurrent collectors. This can be important for robustness and processing.In some embodiments, the maleic anhydride- and/or maleic acid-containingpolymers can be further cross-linked to adjust the viscosity of thesolution and to adjust the char yields. Changes in viscosity can aid incoating and reduce the use of polymer.

As described herein and in copending U.S. case entitled “Method andSystem for Water Based Phenolic Binders for Silicon-Dominant Anodes,”(Inventors Perera, S.; Ji, L.; Ansari, Y.; and Park, B., Ser. No.16/925,111) the entirety of which is hereby incorporated by reference,water-soluble phenolic/resol type polymers (phenolic resins) may becreated by reacting, mixing and/or crosslinking the phenolic resins withdifferent water-soluble polymer crosslinkers or additives such as thedisclosed water-soluble maleic anhydride- and/or maleic acid-containingpolymers/co-polymers, derivatives, and/or combinations. As discussedabove, various combinations of water-soluble polymers can be used asbinders for Si anodes and/or to generate carbon to improve theSi-dominant anode//cathode full cell cycle performance. Such polymersmay have a high carbon yield upon pyrolysis. As disclosed in copendingU.S. case entitled “Method and System for Water Based Phenolic Bindersfor Silicon-Dominant Anodes,” phenolic binders may be blended,crosslinked and/or derivatized to improve the water solubility and watertolerance (the highest amount of water that can be introduced beforephase separation). They may also be crosslinked or co-polymerized withwater-soluble polymer derivatives containing hydrophilic functionalgroups. The use of a water-soluble hydrophilic polymer can significantlyimprove the water tolerance of a phenolic resin blend compared tounmodified phenolic resins. The polymer derivatives containinghydrophilic functional groups used for crosslinking, blending orco-polymerization with phenolic resins may include anhydride and/or acidcontaining polymers such as the disclosed water-soluble maleicanhydride- and/or maleic acid-containing polymers/co-polymers,derivatives, and/or combinations.

As used herein, the term “alkyl” refers to a straight or branched,saturated, aliphatic radical having the number of carbon atomsindicated. The alkyl moiety may be branched or straight chain. Forexample, C1-C6 alkyl includes, but is not limited to, methyl, ethyl,propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl,isopentyl, hexyl, etc. Other alkyl groups include, but are not limitedto heptyl, octyl, nonyl, decyl, etc. Alkyl can include any number ofcarbons, such as 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-10, 1-11,1-12, 1-20, 1-25, 1-30, 2-3, 2-4, 2-5, 2-6, 3-4, 3-5, 3-6, 4-5, 4-6 and5-6. Named alkyl groups include, but are not limited to 1 carbonmeth-(methyl), 2 carbons eth-(ethyl); 3 carbons-prop-(propyl), 4carbons-but-(butyl), 5 carbon pent-(pentyl), 6 carbon hex-(hexyl), 7carbon hept-(heptyl), 8 carbon oct-(octyl), 9 carbon non-(nonyl), 10carbon dec-(decyl), 11 carbon undec-(undecyl), 12 carbon dodec-(dodecyl,also lauryl), 13 carbon tridec-(tridecyl), 14 carbontetradec-(tetradecyl, also myristyl), 15 carbon pentadec-(pentadecyl),16 carbon hexadec-(hexadecyl, cetyl), 17 carbon heptadec-(heptadecyl),18 carbon octadec-(octadecyl, also stearyl), 19 carbonnonadec-(nonadecyl), 20 carbon eicos-(eicosyl, also arachidyl). Thealkyl group is typically monovalent, but can be divalent, such as whenthe alkyl group links two moieties together.

The term “fluoro-alkyl” refers to an alkyl group where one, some, or allhydrogen atoms have been replaced by fluorine.

The term “alkylene” refers to an alkyl group, as defined above, linkingat least two other groups, i.e., a divalent hydrocarbon radical. The twomoieties linked to the alkylene can be linked to the same atom ordifferent atoms of the alkylene. For instance, a straight chain alkylenecan be the bivalent radical of —(CH₂)_(n)—, where n is 1, 2, 3, 4, 5, 6,7, 8, 9, 10 or more. Alkylene groups include, but are not limited to,methylene, ethylene, propylene, isopropylene, butylene, isobutylene,sec-butylene, pentylene and hexylene.

The term “alkoxy” refers to alkyl group having an oxygen atom thateither connects the alkoxy group to the point of attachment or is linkedto two carbons of the alkoxy group. Alkoxy groups include, for example,methoxy, ethoxy, propoxy, iso-propoxy, butoxy, 2-butoxy, iso-butoxy,sec-butoxy, tert-butoxy, pentoxy, hexoxy, etc. The alkoxy groups can befurther substituted with a variety of substituents described within. Forexample, the alkoxy groups can be substituted with halogens to form a“halo-alkoxy” group, or substituted with fluorine to form a“fluoro-alkoxy” group.

The term “alkenyl” refers to either a straight chain or branchedhydrocarbon of 2 to 6 carbon atoms, having at least one double bond.Examples of alkenyl groups include, but are not limited to, vinyl,propenyl, isopropenyl, 1-butenyl, 2-butenyl, isobutenyl, butadienyl,1-pentenyl, 2-pentenyl, isopentenyl, 1,3-pentadienyl, 1,4-pentadienyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 1,3-hexadienyl, 1,4-hexadienyl,1,5-hexadienyl, 2,4-hexadienyl, or 1,3,5-hexatrienyl. Alkenyl groups canalso have from 2 to 3, 2 to 4, 2 to 5, 3 to 4, 3 to 5, 3 to 6, 4 to 5, 4to 6 and 5 to 6 carbons. The alkenyl group is typically monovalent, butcan be divalent, such as when the alkenyl group links two moietiestogether.

The term “alkenylene” refers to an alkenyl group, as defined above,linking at least two other groups, i.e., a divalent hydrocarbon radical.The two moieties linked to the alkenylene can be linked to the same atomor different atoms of the alkenylene. Alkenylene groups include, but arenot limited to, ethenylene, propenylene, isopropenylene, butenylene,isobutenylene, sec-butenylene, pentenylene and hexenylene.

The term “alkynyl” refers to either a straight chain or branchedhydrocarbon of 2 to 6 carbon atoms, having at least one triple bond.Examples of alkynyl groups include, but are not limited to, acetylenyl,propynyl, 1-butynyl, 2-butynyl, isobutynyl, sec-butynyl, butadiynyl,1-pentynyl, 2-pentynyl, isopentynyl, 1,3-pentadiynyl, 1,4-pentadiynyl,1-hexynyl, 2-hexynyl, 3-hexynyl, 1,3-hexadiynyl, 1,4-hexadiynyl,1,5-hexadiynyl, 2,4-hexadiynyl, or 1,3,5-hexatriynyl. Alkynyl groups canalso have from 2 to 3, 2 to 4, 2 to 5, 3 to 4, 3 to 5, 3 to 6, 4 to 5, 4to 6 and 5 to 6 carbons. The alkynyl group is typically monovalent, butcan be divalent, such as when the alkynyl group links two moietiestogether.

The term “alkynylene” refers to an alkynyl group, as defined above,linking at least two other groups, i.e., a divalent hydrocarbon radical.The two moieties linked to the alkynylene can be linked to the same atomor different atoms of the alkynylene. Alkynylene groups include, but arenot limited to, ethynylene, propynylene, butynylene, sec-butynylene,pentynylene and hexynylene.

The term “cycloalkyl” refers to a saturated or partially unsaturated,monocyclic, fused bicyclic, bridged polycyclic, or spiro ring assemblycontaining from 3 to 12, from 3 to 10, or from 3 to 7 ring atoms, or thenumber of atoms indicated. Monocyclic rings include, for example,cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclooctyl.Bicyclic and polycyclic rings include, for example, norbornane,decahydronaphthalene and adamantane. For example, C3-C8 cycloalkylincludes cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl,and norbornane. As used herein, the term “fused” refers to two ringswhich have two atoms and one bond in common. For example, in thefollowing structure, rings A and B are fused

As used herein, the term “bridged polycyclic” refers to compoundswherein the cycloalkyl contains a linkage of one or more atomsconnecting non-adjacent atoms. The following structures

and

are examples of “bridged” rings. As used herein, the term “spiro” refersto two rings which have one atom in common and the two rings are notlinked by a bridge. Examples of fused cycloalkyl groups aredecahydronaphthalenyl, dodecahydro-1H-phenalenyl andtetradecahydroanthracenyl; examples of bridged cycloalkyl groups arebicyclo[1.1.1]pentyl, adamantanyl, and norbornanyl; and examples ofspiro cycloalkyl groups include spiro[3.3]heptane and spiro[4.5]decane.

The term “cycloalkylene” refers to a cycloalkyl group, as defined above,linking at least two other groups, i.e., a divalent hydrocarbon radical.The two moieties linked to the cycloalkylene can be linked to the sameatom or different atoms of the cycloalkylene. Cycloalkylene groupsinclude, but are not limited to, cyclopropylene, cyclobutylene,cyclopentylene, cyclohexylene, and cyclooctylene.

The term “aryl” refers to a monocyclic or fused bicyclic, tricyclic orgreater, aromatic ring assembly containing 6 to 16 ring carbon atoms.For example, aryl may be phenyl, benzyl or naphthyl, preferably phenyl.Aryl groups may include fused multicyclic ring assemblies wherein onlyone ring in the multicyclic ring assembly is aromatic. Aryl groups canbe mono-, di- or tri-substituted by one, two or three radicals.Preferred as aryl is naphthyl, phenyl or phenyl mono- or disubstitutedby alkoxy, phenyl, halogen, alkyl or trifluoromethyl, especially phenylor phenyl-mono- or disubstituted by alkoxy, halogen or trifluoromethyl,and in particular phenyl.

The term “arylene” refers to an aryl group, as defined above, linking atleast two other groups. The two moieties linked to the arylene arelinked to different atoms of the arylene. Arylene groups include, butare not limited to, phenylene.

The term “heteroaryl” refers to a monocyclic or fused bicyclic ortricyclic aromatic ring assembly containing 5 to 16 ring atoms, wherefrom 1 to 4 of the ring atoms are a heteroatom each N, O or S. Forexample, heteroaryl includes pyridyl, indolyl, indazolyl, quinoxalinyl,quinolinyl, isoquinolinyl, benzothienyl, benzofuranyl, furanyl,pyrrolyl, thiazolyl, benzothiazolyl, oxazolyl, isoxazolyl, triazolyl,tetrazolyl, pyrazolyl, imidazolyl, thienyl, or any other radicalssubstituted, especially mono- or di-substituted, by e.g. alkyl, nitro orhalogen. Pyridyl represents 2-, 3- or 4-pyridyl, advantageously 2- or3-pyridyl. Thienyl represents 2- or 3-thienyl. Quinolinyl representspreferably 2-, 3- or 4-quinolinyl. Isoquinolinyl represents preferably1-, 3- or 4-isoquinolinyl. Benzopyranyl, benzothiopyranyl representspreferably 3-benzopyranyl or 3-benzothiopyranyl, respectively. Thiazolylrepresents preferably 2- or 4-thiazolyl, and most preferred 4-thiazolyl.Triazolyl is preferably 1-, 2- or 5-(1,2,4-triazolyl). Tetrazolyl ispreferably 5-tetrazolyl.

Preferably, heteroaryl is pyridyl, indolyl, quinolinyl, pyrrolyl,thiazolyl, isoxazolyl, triazolyl, tetrazolyl, pyrazolyl, imidazolyl,thienyl, furanyl, benzothiazolyl, benzofuranyl, isoquinolinyl,benzothienyl, oxazolyl, indazolyl, or any of the radicals substituted,especially mono- or di-substituted.

The term “heteroalkyl” refers to an alkyl group having from 1 to 3heteroatoms such as N, O and S. The heteroatoms can also be oxidized,such as, but not limited to, —S(O)— and —S(O)₂—. For example,heteroalkyl can include ethers, thioethers, alkyl-amines andalkyl-thiols.

The term “heteroalkylene” refers to a heteroalkyl group, as definedabove, linking at least two other groups. The two moieties linked to theheteroalkylene can be linked to the same atom or different atoms of theheteroalkylene.

The term “heterocycloalkyl” refers to a ring system having from 3 ringmembers to about 20 ring members and from 1 to about 5 heteroatoms suchas N, O and S. The heteroatoms can also be oxidized, such as, but notlimited to, —S(O)— and —S(O)₂—. For example, heterocycle includes, butis not limited to, tetrahydrofuranyl, tetrahydrothiophenyl, morpholino,pyrrolidinyl, pyrrolinyl, imidazolidinyl, imidazolinyl, pyrazolidinyl,pyrazolinyl, piperazinyl, piperidinyl, indolinyl, quinuclidinyl and1,4-dioxa-8-aza-spiro[4.5]dec-8-yl.

The term “heterocycloalkylene” refers to a heterocyclalkyl group, asdefined above, linking at least two other groups. The two moietieslinked to the heterocycloalkylene can be linked to the same atom ordifferent atoms of the heterocycloalkylene.

The term “optionally substituted” is used herein to indicate a moietythat can be unsubstituted or substituted by one or more substituent.When a moiety term is used without specifically indicating assubstituted, the moiety is unsubstituted.

In accordance with the disclosure, maleic anhydride- and/or maleicacid-containing polymers/co-polymers may be in alkali salt form. Alkalisalts are those salts having an alkali metal counterion. The alkalimetals are those in Group 1 of the Periodic Table, specifically, lithium(Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), andfrancium (Fr). Group 1 also includes hydrogen (H). In salts, thesealkali metals appear as alkali metal ions (such as Nat). In someembodiments, the salt is a sodium salt. In other embodiments, the saltis a lithium salt.

In accordance with the disclosure, water-soluble maleicanhydride-containing polymers, including alternating co-polymers such asPoly(methyl vinyl ether-alt-maleic anhydride) (PMVMA) may be used asbinders for Si dominant anodes. In some embodiments, the polymer hasdifferent molecular weights or is further derivatized. A generalPoly(methyl vinyl ether-alt-maleic anhydride) (PMVMA) structure (I) isshown below:

In some embodiments, n may be >10; in other embodiments, n maybe >100, >1,000, >10,000 or >100,000.

In other embodiments, water-soluble maleic anhydride-containingpolymers, including alternating co-polymers such as Poly(alkyl vinylether-alt-maleic anhydride) may be used as binders for Si dominantanodes. In some embodiments, the polymer has different molecular weightsor is further derivatized. A general Poly(alkyl vinyl ether-alt-maleicanhydride) structure (Ia) is shown below:

In some embodiments, n may be >10; in other embodiments, n maybe >100, >1,000, >10,000 or >100,000. In some embodiments, R may be H oralkyl as defined above. In other embodiments, R may be selected from thegroup consisting of H, alkyl, fluoro-alkyl, alkylene, alkoxy, alkenyl,alkenylene, alkynyl, alkynylene, cycloalkyl, cycloalkylene, aryl,arylene, heteroaryl, heteroalkyl, heteroalkylene, heterocycloalkyl, andheterocycloalkylene, as defined above, which may be also optionallysubstituted.

In accordance with the disclosure, water-soluble maleic acid-containingpolymers such as Poly(methyl vinyl ether-alt-maleic acid) may be used asbinders for Si dominant anodes. In some embodiments, the polymer hasdifferent molecular weights or is further derivatized. A generalPoly(methyl vinyl ether-alt-maleic acid) structure (II) is shown below:

In some embodiments, n may be >10; in other embodiments, n maybe >100, >1,000, >10,000 or >100,000.

In other embodiments, water-soluble maleic acid-containing polymers suchas Poly(alkyl vinyl ether-alt-maleic acid) may be used as binders for Sidominant anodes. In some embodiments, the polymer has differentmolecular weights or is further derivatized. A general Poly(alkyl vinylether-alt-maleic acid) structure (IIa) is shown below:

In some embodiments, n may be >10; in other embodiments, n maybe >100, >1,000, >10,000 or >100,000. In some embodiments, R may be H oralkyl as defined above. In other embodiments, R may be selected from thegroup consisting of H, alkyl, fluoro-alkyl, alkylene, alkoxy, alkenyl,alkenylene, alkynyl, alkynylene, cycloalkyl, cycloalkylene, aryl,arylene, heteroaryl, heteroalkyl, heteroalkylene, heterocycloalkyl, andheterocycloalkylene, as defined above, which may be also optionallysubstituted.

In accordance with the disclosure, water-soluble maleic acid-containingco-polymers such as Poly(acrylic acid-co-maleic acid) may be used asbinders for Si dominant anodes. In some embodiments, the polymer hasdifferent molecular weights or is further derivatized. A generalPoly(acrylic acid-co-maleic acid) structure (III) is shown below:

In some embodiments, x and/or y may be >10; in other embodiments, xand/or y may be >100, >1,000, >10,000 or >100,000.

In accordance with the disclosure, salts of water-soluble maleicacid-containing co-polymers such as Poly(acrylic acid-co-maleic acid)sodium salt may be used as binders for Si dominant anodes. In someembodiments, the polymer has different molecular weights or is furtherderivatized. A general Poly(acrylic acid-co-maleic acid) salt structure(IV) is shown below:

In some embodiments, x and/or y may be >10; in other embodiments, xand/or y may be >100, >1,000, >10,000 or >100,000. In some embodiments,each R may be the same or different and may be H or an alkali metal ionsuch as sodium (Na), as defined above. In other embodiments, each R maybe the same or different and may be selected from the group consistingof an alkali metal ion, H, alkyl, fluoro-alkyl, alkylene, alkoxy,alkenyl, alkenylene, alkynyl, alkynylene, cycloalkyl, cycloalkylene,aryl, arylene, heteroaryl, heteroalkyl, heteroalkylene,heterocycloalkyl, and heterocycloalkylene, as defined above, which maybe also optionally substituted.

In accordance with the disclosure, salts of water-soluble maleicacid-containing alternating co-polymers such as Poly(styrene-alt-maleicacid) sodium salt may be used as binders for Si dominant anodes. In someembodiments, the polymer has different molecular weights or is furtherderivatized. A general Poly(styrene-alt-maleic acid) salt structure (V)is shown below:

In some embodiments, x and/or y may be >10; in other embodiments, xand/or y may be >100, >1,000, >10,000 or >100,000. In some embodiments,each R may be the same or different and may be H or an alkali metal ionsuch as sodium (Na), as defined above. In other embodiments, each R maybe the same or different and may be selected from the group consistingof an alkali metal ion, H, alkyl, fluoro-alkyl, alkylene, alkoxy,alkenyl, alkenylene, alkynyl, alkynylene, cycloalkyl, cycloalkylene,aryl, arylene, heteroaryl, heteroalkyl, heteroalkylene,heterocycloalkyl, and heterocycloalkylene, as defined above, which maybe also optionally substituted.

In accordance with the disclosure, water-soluble maleic acid-containingalternating co-polymers such as Poly(styrene-co-maleic acid), which maybe partially or fully esterified (e.g. isobutyl ester, methyl esterand/or combinations thereof) may be used as binders for Si dominantanodes. In some embodiments, the polymer has different molecular weightsor is further derivatized. A general Poly(styrene-co-maleic acid)structure (VI) is shown below:

In some embodiments, x and/or y may be >10; in other embodiments, xand/or y may be >100, >1,000, >10,000 or >100,000. In some embodiments,each R may be the same or different and may be H or alkyl, as definedabove. In other embodiments, each R may be the same or different and maybe H or CH₃ or

or

In further embodiments, each R may be the same or different and may beselected from the group consisting of H, alkyl, fluoro-alkyl, alkylene,alkoxy, alkenyl, alkenylene, alkynyl, alkynylene, cycloalkyl,cycloalkylene, aryl, arylene, heteroaryl, heteroalkyl, heteroalkylene,heterocycloalkyl, and heterocycloalkylene, as defined above, which maybe also optionally substituted.

In accordance with the disclosure, water-soluble maleicanhydride-containing alternating co-polymers such asPoly(styrene-alt-maleic anhydride) may be used as binders for Sidominant anodes. In some embodiments, the polymer has differentmolecular weights or is further derivatized. A generalPoly(styrene-alt-maleic anhydride) structure (VII) is shown below:

In some embodiments, m and/or n may be >10; in other embodiments, mand/or n may be >100, >1,000, >10,000 or >100,000.

In accordance with the disclosure, water-soluble maleicanhydride-containing alternating co-polymers such asPoly(alkylene-alt-maleic anhydride) may be used as binders for Sidominant anodes. In some embodiments, the polymer has differentmolecular weights or is further derivatized. A generalPoly(alkylene-alt-maleic anhydride) structure (VII) is shown below:

In some embodiments, n may be >10; in other embodiments, n maybe >100, >1,000, >10,000 or >100,000. In some embodiments, each R₁, R₂and R₃ may be the same or different and may be H or alkyl as definedabove. In some embodiments, R₁=CH₂(CH₂)_(x)CH₃, where x=1-20. In certainembodiments, the water-soluble maleic anhydride-containing alternatingco-polymer may be Poly(isobutylene-alt-maleic anhydride) {R₁=H, R₂ andR₃=CH₃}; Poly(maleic anhydride-alt-1-octadecene){R₁=octadecane/octadecene (i.e. C18 chain), R₂ and R₃=H}; orPoly(ethylene-alt-maleic anhydride) {R₁, R₂ and R₃=H}. In furtherembodiments, each R₁, R₂ and R₃ may be the same or different and may beselected from the group consisting of H, alkyl, fluoro-alkyl, alkylene,alkoxy, alkenyl, alkenylene, alkynyl, alkynylene, cycloalkyl,cycloalkylene, aryl, arylene, heteroaryl, heteroalkyl, heteroalkylene,heterocycloalkyl, and heterocycloalkylene, as defined above, which maybe also optionally substituted.

In accordance with the disclosure, water-soluble maleicanhydride-containing grafted polymers such as water-solublePolyalkylene-graft-maleic anhydride may be used as binders for Sidominant anodes. In some embodiments, the polymer has differentmolecular weights or is further derivatized. A generalPolyalkylene-graft-maleic anhydride structure (IX) is shown below:

In some embodiments, m and/or n may be >10; in other embodiments, mand/or n may be >100, >1,000, >10,000 or >100,000. In some embodiments,each R₁, R₂, R₃ and R₄ may be the same or different and may be H oralkyl as defined above. In certain embodiments, the water-solublePolyalkylene-graft-maleic anhydride may be Polyethylene-graft-maleicanhydride {R₁, R₂, R₃ and R₄=H} or Polypropylene-graft-maleic anhydride{R₁=H, R₂=CH₃, R₃=H and R₄=CH₃}. In further embodiments, each R₁, R₂, R₃and R₄ may be the same or different and may be selected from the groupconsisting of H, alkyl, fluoro-alkyl, alkylene, alkoxy, alkenyl,alkenylene, alkynyl, alkynylene, cycloalkyl, cycloalkylene, aryl,arylene, heteroaryl, heteroalkyl, heteroalkylene, heterocycloalkyl, andheterocycloalkylene, as defined above, which may be also optionallysubstituted.

In accordance with the disclosure, water-soluble maleicanhydride-containing grafted/block polymers such as water-solublePolyalkene-graft-maleic anhydride may be used as binders for Si dominantanodes. In some embodiments, the polymer has different molecular weightsor is further derivatized. A general Polyalkene-graft-maleic anhydride(X) is shown below:

In some embodiments, m and/or n may be >10; in other embodiments, mand/or n may be >100, >1,000, >10,000 or >100,000. In some embodiments,R may be H or alkyl, as defined above. In certain embodiments, thewater-soluble Polyalkene-graft-maleic anhydride may bePolyisoprene-graft-maleic anhydride {R=CH₃}. In other embodiments, R maybe selected from the group consisting of H, alkyl, fluoro-alkyl,alkylene, alkoxy, alkenyl, alkenylene, alkynyl, alkynylene, cycloalkyl,cycloalkylene, aryl, arylene, heteroaryl, heteroalkyl, heteroalkylene,heterocycloalkyl, and heterocycloalkylene, as defined above, which maybe also optionally substituted.

In accordance with the disclosure, water-soluble maleicanhydride-containing grafted/block polymers such as water-solublePolystyrene-block-poly(alkylene-ran-butylene)-block-polystyrene-graft-maleicanhydride may be used as binders for Si dominant anodes. In someembodiments, the polymer has different molecular weights or is furtherderivatized. A generalPolystyrene-block-poly(alkylene-ran-butylene)-block-polystyrene-graft-maleicanhydride structure (XI) is shown below:

In some embodiments, w, x, y and/or z may be >10; in other embodiments,w, x, y and/or z may be >100, >1,000, >10,000 or >100,000. In someembodiments, R may be H or alkyl, as defined above. In certainembodiments, the water-soluble maleic anhydride-containing alternatingco-polymer may bePolystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleicanhydride {R=CH₃}. In other embodiments, R may be selected from thegroup consisting of H, alkyl, fluoro-alkyl, alkylene, alkoxy, alkenyl,alkenylene, alkynyl, alkynylene, cycloalkyl, cycloalkylene, aryl,arylene, heteroaryl, heteroalkyl, heteroalkylene, heterocycloalkyl, andheterocycloalkylene, as defined above, which may be also optionallysubstituted.

Further functional compounds may be used as crosslinkers or additives tothe above-described water-soluble maleic anhydride- and/or maleicacid-containing polymer binder compositions. In some embodiments,compositions containing the various components are utilized; in otherembodiments, the further functional compounds may serve as acrosslinkers and/or be copolymerized with the water-soluble maleicanhydride- and/or maleic acid-containing polymer. In some embodiments,functional compounds may be used to crosslink the polymers, providingchanges to the functionality and molecular weights and thus theproperties of the polymer binder. The crosslinkers or additives may beused in different concentrations such as 1% to 100% relative to thepolymer binders for various types of Si anodes. Concentrations ofadditives may be about 1 wt % to 100 wt % relative to the polymers asbinders. In some embodiments, the concentration may be 1 wt % to 50 wt %relative to the polymer binders; in other embodiments, the concentrationmay be 10 wt % to 40 wt % relative to the polymer binders. In otherembodiments, the concentration may be 1 wt % to 20 wt % relative to thepolymer binders. In other embodiments, the concentration may be 1 wt %to 10 wt % relative to the polymer binders In further embodiments, theconcentration may be 1 wt % to 5 wt % relative to the polymer binders.

Additives include, but are not limited to, one or more functionalcompound additives such as polymers, water-soluble polymers,cyclodextrin-based compounds, tannic acid (and/or other polyphenols),nitrogen-containing compounds and sulfur-containing compounds; and/orconductive additives; as described below.

In some embodiments, further functional compounds used with thewater-soluble maleic anhydride- and/or maleic acid-containing polymerbinders include functional Cyclodextrin-based compounds (includingdifferent types of functional α-Cyclodextrin, β-Cyclodextrin,β-Cyclodextrin compounds, etc.). The functional cyclodextrin-basedcompounds may be used as crosslinkers to further improve the viscosityof the maleic anhydride- and/or maleic acid-containing polymer bindersolution and/or to enhance the interactions of the polymers with Sipowders.

In some embodiments, further functional compounds that may be used ascrosslinkers or additives are functional aliphatic and aromaticnitrogen-containing compounds including primary amines (R′NH₂),secondary amines (R′R″NH), secondary heterocyclic amines and/or iminesor amides. In some embodiments, the compound is selected fromPutrescine, Spermidine, Spermine, Thermospermine, Polyethylenimine(PEI), N,N′-Methylenebisacrylamide (MBAA), or N,N′-Ethylenebisacrylamide(EBAA), as shown below. These nitrogen-containing compounds include, butare not limited to, the following:

In some embodiments, further functional compounds that may be used ascrosslinkers or additives are polyphenol compounds including, but notlimited to Tannic acid.

Other polyphenols may also be used such as flavonoids (e.g. quercetin,kaempferol, catechins, anthocyanins), phenolic acids (e.g. stilbenes,lignans), polyphenolic amides (e.g. capsaicinoids, avenanthramides),resveratrol, ellagic acid, curcumin and lignans.

In some embodiments, further functional compounds that may be used ascrosslinkers or additives are functional aliphatic and aromatic epoxycompounds. In some embodiments, the compound is selected fromPoly(ethylene glycol) diglycidyl ether, Trimethylolpropane triglycidylether, Tris(4-hydroxyphenyl)methane triglycidyl ether,Tris(2,3-epoxypropyl) isocyanurate, or Poly[(o-cresyl glycidylether)-co-formaldehyde], as shown below. These epoxy compounds include,but are not limited to, the following:

In some embodiments, further functional compounds that may be used ascrosslinkers or additives are functional sulfur-containing compounds. Insome embodiments, the compound is selected from Trimethylolpropanetris(3-mercaptopropionate), Pentaerythritoltetrakis(3-mercaptopropionate), 2,2′-(Ethylenedioxy)diethanethiol,1,2-Ethanedithiol, 1,4-Butanedithiol, as shown below. Thesesulfur-containing compounds include, but are not limited to, thefollowing:

In some embodiments, the additives can be used along with thewater-soluble maleic anhydride- and/or maleic acid-containing polymersin the creation of the electrode. Additives include, but are not limitedto, one or more conductive additives and/or functional compoundadditives such as polymers, water-soluble polymers, cyclodextrin-basedcompounds, tannic acid, nitrogen-containing compounds andsulfur-containing compounds, and/or other compounds, as describedherein. Concentrations of additives may be about 1 wt % to 100 wt %relative to the polymers as binders. In some embodiments, theconcentration may be 1 wt % to 50 wt % relative to the polymer binders;in other embodiments, the concentration may be 10 wt % to 40 wt %relative to the polymer binders. In other embodiments, the concentrationmay be 1 wt % to 20 wt % relative to the polymer binders. In otherembodiments, the concentration may be 1 wt % to 10 wt % relative to thepolymer binders In further embodiments, the concentration may be 1 wt %to 5 wt % relative to the polymer binders. One or more additives can beused. In some embodiments, a conductive additive and a functionalcompound additive are used together with the water-soluble maleicanhydride- and/or maleic acid-containing polymer/co-polymer.

In some embodiments, conductive additives, such as Super P carbon black,graphite, graphene, carbon nanofibers, carbon fibers, carbon nanotubes,porous carbons and other types of zero-, one-, two-, three-dimensionalcarbon materials can be added into all of the aforementioned systems asconductive additives for different types of Si anodes. The presentlydescribed functional binders can promote the dispersion of Si activematerials and conductive additive(s), while providing good connectionsand strong adhesion to metal current collectors. Concentrations ofadditives may be about 1 wt % to 100 wt % relative to the polymers asbinders. In some embodiments, the concentration may be 1 wt % to 50 wt %relative to the polymer binders; in other embodiments, the concentrationmay be 10 wt % to 40 wt % relative to the polymer binders. In otherembodiments, the concentration may be 1 wt % to 20 wt % relative to thepolymer binders. In other embodiments, the concentration may be 1 wt %to 10 wt % relative to the polymer binders In further embodiments, theconcentration may be 1 wt % to 5 wt % relative to the polymer binders.

In some embodiments, further functional compound additives such aspolymers can be used in combination with the water-soluble maleicanhydride- and/or maleic acid-containing polymer binders for Si dominantanodes. Functional compound additive polymers include, but are notlimited to, other water-soluble polymers, such as Poly(acrylic acid)(PAA), Poly(vinyl alcohol) (PVA or PVOH), Lignin, styrene-butadienerubber (SBR), Gelatin, Carboxymethyl cellulose (CMC), Chitosan,Alginate, Pectin, Amylose, Starch, Gums (Xanthan, Arabic, Gelan, Karaya,Guar). In further embodiments, other functional compound additivepolymers such as phenolic/resol type polymers (phenolic resins) can bemade water-soluble by using in combination with the water-soluble maleicanhydride- and/or maleic acid-containing polymers disclosed herein (suchas by crosslinking the compounds). Concentrations of additives may beabout 1 wt % to 100 wt % relative to the polymers as binders. In someembodiments, the concentration may be 1 wt % to 50 wt % relative to thepolymer binders; in other embodiments, the concentration may be 10 wt %to 40 wt % relative to the polymer binders. In other embodiments, theconcentration may be 1 wt % to 20 wt % relative to the polymer binders.In other embodiments, the concentration may be 1 wt % to 10 wt %relative to the polymer binders. In further embodiments, theconcentration may be 1 wt % to 5 wt % relative to the polymer binders.

In accordance with the disclosure, water-soluble maleic anhydride-and/or maleic acid-containing polymers/co-polymers, derivatives, and/orcombinations are used as binders for Si anodes to improve theSi-dominant anode//cathode full cell cycle performance. Thesewater-soluble maleic anhydride- and/or maleic acid-containingpolymers/co-polymers, derivatives, and/or combinations include, but arenot limited to Poly(methyl vinyl ether-alt-maleic anhydride);Poly(methyl vinyl ether-alt-maleic acid); Poly(acrylic acid-co-maleicacid); Poly(acrylic acid-co-maleic acid) sodium salts;Poly(styrene-alt-maleic acid) sodium salts; Poly(styrene-co-maleicacid), partial isobutyl esters; Poly(styrene-co-maleic acid), partialisobutyl/methyl mixed esters; Poly(styrene-alt-maleic anhydride),partial methyl esters; Poly(isobutylene-alt-maleic anhydride);Poly(maleic anhydride-alt-1-octadecene); Poly(ethylene-alt-maleicanhydride); Polyethylene-graft-maleic anhydride;Polypropylene-graft-maleic anhydride; Polyisoprene-graft-maleicanhydride; and/orPolystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleicanhydride. Polymers may have varying molecular weights. These polymersmay be fully or partially carbonized (pyrolyzed).

Water-soluble maleic anhydride- and/or maleic acid-containingpolymers/co-polymers, derivatives, and/or combinations are used asbinders for various anodes such as anode-based Li-ion batteries,including Si anode-based and directly coated Si-dominant anodes. In afurther embodiment, the binders may be used to treat graphite (carbon)anode-based Li-ion batteries, including hard/soft carbon. In anotherembodiment, the binders may be used to treat other anode-based Li-ionbatteries. These anodes may be Sn, Sb, P, transition metal oxides, etc.In some embodiments, the anode comprises an active material thatcomprises between 50% to 95% silicon. In some embodiments, the activematerial comprises more than 70% Si.

In some embodiments, electrodes may be made by adding the water-solublemaleic anhydride- and/or maleic acid-containing polymer binders, asdescribed above, along with any additives, into the electrode slurry ordepositing on an electrode active material (i.e., electrode coatinglayer) when creating the additive-containing electrodes. Aqueoussolutions of the polymer binders are prepared, which are used to createthe slurry, which then may be used for coating the electrode. In someembodiments, the above procedure is used to make Si anode-based ordirectly coated Si-dominant anodes, etc. having a water-soluble maleicanhydride- and/or maleic acid-containing polymer binder.

In some embodiments, the polymer binder-containing Si anode materials asdescribed above may be carbonized through pyrolysis of the polymer. Acarbon network may be formed via carbonization of the binders through aheat treatment of the electrode (pyrolysis). This network enhances theelectrode conductivity and mechanical properties of the as-fabricated Sianodes. Pyrolysis may be full or partial. Carbonized polymers can serveas both a binder and a conductive additive and show less aggregationcompared to conventional carbon conductive additives. Pyrolysis may becarried out by heating to 500-1200° C. In some embodiments, pyrolysismay be carried out by heating to 500-800° C.

The below example devices and processes for device fabrication generallydescribed below, and the performances of lithium ion batteries withdifferent water-soluble maleic anhydride- and/or maleic acid-containingpolymer binders are evaluated.

Aqueous solutions of water-soluble maleic anhydride- and/or maleicacid-containing polymers (with or without further additives) may be madeat varying concentrations. Concentrations may be about 1 wt % to 90 wt%. In some embodiments, the concentration may be 1 wt % to 50 wt % indeionized (DI) water; in other embodiments, the concentration may be 10wt % to 40 wt %; in further embodiments, the concentration may be 10 wt% to 30 wt %. In one embodiment; Poly(methyl vinyl ether-alt-maleicanhydride) (PMVMA) may be made into a 20 wt % aqueous solution in DIwater, as shown in FIG. 3. In the present disclosure, water-solublemaleic anhydride- and/or maleic acid-containing polymers such as PMVMAhave very good dissolution in water due to the existence of polar groupsin their molecular structures which can have strong interactions withH₂O molecules.

In accordance with the disclosure, electrodes using the binders asdisclosed herein show less aggregation as compared to conventionalcarbon conductive additives. Electrodes may be made by adding thewater-soluble maleic anhydride- and/or maleic acid-containing polymerbinders, as described above, along with any additives, into theelectrode slurry. A photo of a direct coated Si anode using a 20 wt %Poly(methyl vinyl ether-alt-maleic anhydride) (PMVMA) aqueous solutionas binder is shown in FIG. 4. The photo indicates that the Si powderscan be homogeneously dispersed into the polymer phase and there are noclear Si agglomerates or clusters.

In some embodiments, the polymer binder-containing Si anodes may befurther carbonized through pyrolysis of the polymer to form a carbonnetwork. FIG. 5 shows Thermogravimetric Analysis (TGA) curves ofPoly(methyl vinyl ether-alt-maleic anhydride) (PMVMA) under Argon. TheTGA curve indicates that the PMVMA can have about 25 wt % char yieldeven after pyrolysis at 800° C. Pyrolysis may be full or partial.Carbonized polymers can serve as both a binder and a conductive additiveand show less aggregation compared to conventional carbon conductiveadditives.

In accordance with the disclosure, water-soluble maleic anhydride-and/or maleic acid-containing polymers serve as superior binders foranodes in making Si anodes. FIG. 6 shows an adhesion test for a Cu anodepyrolyzed at 700° C. utilizing PMVMA as binder. The anode shows asuperior capability of holding >250 grams of weight before the coatingdetaches from the copper. In this test, the adhesive tape holding theanode on one side and the glass slide on the other may be a double-sidedScotch tape (½″ Scotch® Double Sided Tape Dispensered Rolls) with awidth of 1.27 cm. Such adhesion is much higher than most binder-freeanodes, which mostly fail to hold more than 50 grams of weight.

As discussed above, expansion of the silicon active material can resultin poor cycle life due to cracking. For example, silicon can swell inexcess of 300% upon lithium insertion. The use of water-soluble maleicanhydride- and/or maleic acid-containing polymers as binders asdisclosed for Si anodes allows for free spaces to be created among Siparticles during the pyrolysis process. These free spaces allow for thenecessary expansion, creating the extra volume required for Si expansionduring cycling. FIG. 7 is a photo showing the result of a winding testfor a Si anode pyrolyzed at 700° C. with PMVMA as binder. In this test,the anode may be wrapped around a 4 mm mandrel in order to test thefeasibility of using it for cylindrical cells. As it can be seen fromthe image in FIG. 7, the anode shows minor cracks, no copper exposuredue to carbon detachment, and no flaking. Thus, in accordance with thedisclosure, water-soluble maleic anhydride- and/or maleicacid-containing polymers serve as superior binders for anodesdemonstrate remarkable flexibility and maintenance of anode integritymaking them appropriate for use in cylindrical cells.

FIG. 8. Capacity retention (FIG. 8A) and Normalized capacity retention(FIG. 8B) curves of: (dotted line) standard Si anode//NCA cathode fullcells—Control; and (solid line) as-fabricated Si anode//NCA cathode fullcells. The standard Si anodes may contain about 80 wt % Si, 5 wt %graphite and 15 wt % glass carbon (from resin), and may be laminated on15 μm Cu foil. The average loading is about 2-5 mg/cm². The Si anodesmay be prepared by mixing Si powders with 20 wt % PMVMA aqueoussolution, then the as-prepared Si slurry may be coated on the surface of20 μm Cu foil followed by annealing (pyrolyzing) at 550° C. for 1 hour.The final Si anodes contain about 90 wt % Si, and 10 wt % pyrolyzedcarbon (from PMVMA). The average loading may be about 2-6 mg/cm². Thecathodes may contain about 92 wt % NCA, 4 wt % conductive carbon and 4wt % PVDF, and may be coated on 15 μm Al foil. The average loading maybe about 20-30 mg/cm². The electrolytes used may be 1.2M LiPF₆ inFEC/EMC (3/7 wt %).

The long-term cycling program for these cells may include: (i) At the1st cycle, Charge at 0.33C to 4.2 V until 0.05C, rest 5 minutes,discharge at 0.33C to 3 V, rest 5 minutes; and (ii) from the 2nd cycle,Charge at 4C to 4.2 V until 0.05C, rest 5 minutes, discharge at 0.5C to3.1 V, rest 5 minutes. After every 100 cycles, the test conditions inthe 1st cycle may be repeated.

FIG. 8 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. The manufacturing processes ofthe as-fabricated Si anodes having water-soluble maleic anhydride-and/or maleic acid-containing polymers as binders (with or withoutfurther additives) are relatively simple and low cost. In addition, forthe fabrication of Si-dominant anodes, toxic solvents such as NMP areavoided, and the process is environmentally friendly. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich is complicated, expensive and eco-unfriendly.

FIG. 9. Capacity retention (FIG. 9A) and Normalized capacity retention(FIG. 9B) curves of: (dotted line) the standard Si anode//NCA cathodefull cells—Control; and (solid line) the as-fabricated Si anode//NCAcathode full cells. The standard Si anodes contain about 80 wt % Si, 5wt % graphite and 15 wt % glass carbon (from resin), and may belaminated on 15 μm Cu foil. The average loading maybe about 2-5 mg/cm².The Si anodes may be prepared by mixing Si powders with 20 wt % PMVMAaqueous solution, then the as-prepared Si slurry may be coated on thesurface of 20 μm Cu foil. After that, a very thin polyethylenimine (PEI)layer may be further coated followed by annealing (pyrolyzing) at 700°C. for 1 hour. The final Si anodes contain about 90 wt % Si, and 10 wt %pyrolyzed carbon (from PMVMA and the PEI coating layer). The averageloading may be about 2-6 mg/cm². The cathodes contain about 92 wt % NCA,4 wt % conductive carbon and 4 wt % PVDF, and may be coated on 15 μm Alfoil. The average loading may be about 20-30 mg/cm². The electrolytesused may be 1.2M LiPF₆ in FEC/EMC (3/7 wt %).

The long-term cycling program for these cells may be the same as shownin FIG. 8.

FIG. 9 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. As discussed above, the Sianodes using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders (with or without further additives)as disclosed herein are relatively inexpensive and are straightforwardto make. The as-fabricated Si-dominant anodes are eco-friendly as theyare made using aqueous solutions, thus avoiding toxic solvents. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich may be undesirable, for the reasons discussed above.

FIG. 10. Capacity retention (FIG. 10A) and Normalized capacity retention(FIG. 10B) curves of: (dotted line) the standard Si anode//NCA cathodefull cells—Control; and (solid line) the as-fabricated Si anode//NCAcathode full cells. The standard Si anodes contain about 80 wt % Si, 5wt % graphite and 15 wt % glass carbon (from resin), and may belaminated on 15 μm Cu foil. The average loading may be about 2-5 mg/cm².The as-fabricated Si anodes may be prepared by mixing Si powders with 20wt % PMVMA aqueous solution, then the as-prepared Si slurry may becoated on the surface of 20 μm Cu foil followed by annealing(pyrolyzing) at 700° C. for 1 hour. The final Si anodes contain about 90wt % Si, and 10 wt % pyrolyzed carbon (from PMVMA binder). The averageloading may be about 2-6 mg/cm². The cathodes contain about 92 wt % NCA,4 wt % conductive carbon and 4 wt % PVDF, and may be coated on 15 μm Alfoil. The average loading may be about 20-30 mg/cm². The electrolytesused may be 1.2M LiPF₆ in FEC/EMC (3/7 wt %).

The long-term cycling program for these cells may be the same as shownin FIG. 8.

FIG. 10 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. As discussed above, the Sianodes using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders (with or without further additives)as disclosed herein are relatively inexpensive and are straightforwardto make. The as-fabricated Si-dominant anodes are eco-friendly as theyare made using aqueous solutions, thus avoiding toxic solvents. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich may be undesirable, for the reasons discussed above.

FIG. 11. Capacity retention (FIG. 11A) and Normalized capacity retention(FIG. 11B) curves of: (dotted line) the standard Si anode//NCA cathodefull cells—Control; and (solid line) the as-fabricated Si anode//NCAcathode full cells. The standard Si anodes contain about 80 wt % Si, 5wt % graphite and 15 wt % glass carbon (from resin), and may belaminated on 15 μm Cu foil. The average loading may be about 2-5 mg/cm².The as-fabricated Si anodes may be prepared by mixing Si powders with 20wt % PMVMA & β-Cyclodextrin (β-CD) (9/1 wt %) aqueous solution, then theas-prepared Si slurry may be coated on the surface of 20 μm Cu foilfollowed by annealing at 700° C. for 1 hour. The final Si anodes containabout 90 wt % Si, and 10 wt % pyrolyzed carbon (from PMVMA & β-CD (9/1wt %) binders). The average loading may be about 2-6 mg/cm². Thecathodes contain about 92 wt % NCA, 4 wt % conductive carbon and 4 wt %PVDF, and may be coated on 15 μm Al foil. The average loading may beabout 20-30 mg/cm². The electrolytes used may be 1.2M LiPF₆ in FEC/EMC(3/7 wt %).

The long-term cycling program for these cells may be the same as shownin FIG. 8.

FIG. 11 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. As discussed above, the Sianodes using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders (with or without further additives)as disclosed herein are relatively inexpensive and are straightforwardto make. The as-fabricated Si-dominant anodes are eco-friendly as theyare made using aqueous solutions, thus avoiding toxic solvents. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich may be undesirable, for the reasons discussed above.

FIG. 12. Capacity retention (FIG. 12A) and Normalized capacity retention(FIG. 12B) curves of: (dotted line) the standard Si anode//NCA cathodefull cells—Control; and (solid line) the as-fabricated Si anode//NCAcathode full cells. The standard Si anodes contain about 80 wt % Si, 5wt % graphite and 15 wt % glass carbon (from resin), and may belaminated on 15 μm Cu foil. The average loading may be about 2-5 mg/cm².The as-fabricated Si anodes may be prepared by mixing Si powders with 20wt % PMVMA & Tannic Acid (2/1 wt %) aqueous solution, then coating theas-prepared Si slurry on the surface of 20 μm Cu foil followed byannealing at 700° C. for 1 hour. The final Si anodes contain about 90 wt% Si, and 10 wt % pyrolyzed carbon (from PMVMA & Tannic Acid (2/1 wt %)binders). The average loading may be about 2-6 mg/cm². The cathodescontain about 92 wt % NCA, 4 wt % conductive carbon and 4 wt % PVDF, andmay be coated on 15 μm Al foil. The average loading may be about 20-30mg/cm². The electrolytes used may be 1.2M LiPF₆ in FEC/EMC (3/7 wt %).

The long-term cycling program for these cells may be the same as shownin FIG. 8.

FIG. 12 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. As discussed above, the Sianodes using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders (with or without further additives)as disclosed herein are relatively inexpensive and are straightforwardto make. The as-fabricated Si-dominant anodes are eco-friendly as theyare made using aqueous solutions, thus avoiding toxic solvents. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich may be undesirable, for the reasons discussed above.

FIG. 13. Capacity retention (FIG. 13A) and Normalized capacity retention(FIG. 13B) curves of: (dotted line) the standard Si anode//NCA cathodefull cells—Control; and (solid line) the as-fabricated Si anode//NCAcathode full cells. The standard Si anodes contain about 80 wt % Si, 5wt % graphite and 15 wt % glass carbon (from resin), and may belaminated on 15 μm Cu foil. The average loading is about 2-5 mg/cm². Theas-fabricated Si anodes may be prepared by mixing Si powders, 20 wt %PMVMA & Tannic Acid (2/1 wt %) aqueous solution, and 1 wt % Super P,then coating the as-prepared Si slurry on the surface of 20 μm Cu foilfollowed by annealing at 700° C. for 1 hour. The final Si anodes containabout 90 wt % Si, 1 wt % Super P, and 9 wt % pyrolyzed carbon (fromPMVMA & Tannic Acid (2/1 wt %)). The average loading may be about 2-6mg/cm². The cathodes contain about 92 wt % NCA, 4 wt % conductive carbonand 4 wt % PVDF, and may be coated on 15 μm Al foil. The average loadingmay be about 20-30 mg/cm². The electrolytes used may be 1.2M LiPF₆ inFEC/EMC (3/7 wt %).

The long-term cycling program for these cells may be the same as shownin FIG. 8.

FIG. 13 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. As discussed above, the Sianodes using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders (with or without further additives)as disclosed herein are relatively inexpensive and are straightforwardto make. The as-fabricated Si-dominant anodes are eco-friendly as theyare made using aqueous solutions, thus avoiding toxic solvents. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich may be undesirable, for the reasons discussed above.

FIG. 14. Capacity retention (FIG. 14A) and Normalized capacity retention(FIG. 14B) curves of: (dotted line) the standard Si anode//NCA cathodefull cells—Control; and (solid line) the as-fabricated Si anode//NCAcathode full cells. The standard Si anodes contain about 80 wt % Si, 5wt % graphite and 15 wt % glass carbon (from resin), and may belaminated on 15 μm Cu foil. The average loading may be about 2-5 mg/cm².The as-fabricated Si anodes may be prepared by mixing Si powders, 20 wt% PMVMA & Tannic Acid (2/1 wt %) aqueous solution, and 2 wt % Super P,then coating the as-prepared Si slurry on the surface of 20 μm Cu foilfollowed by annealing at 550° C. for 1 hour. The final Si anodes containabout 90 wt % Si, 2 wt % Super P, and 8 wt % pyrolyzed carbon (fromPMVMA & Tannic Acid (2/1 wt %) binders). The average loading may beabout 2-6 mg/cm². The cathodes contain about 92 wt % NCA, 4 wt %conductive carbon and 4 wt % PVDF, and may be coated on 15 μm Al foil.The average loading may be about 20-30 mg/cm². The electrolytes used maybe 1.2M LiPF₆ in FEC/EMC (3/7 wt %).

The long-term cycling program for these cells may be the same as shownin FIG. 8.

FIG. 14 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. As discussed above, the Sianodes using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders (with or without further additives)as disclosed herein are relatively inexpensive and are straightforwardto make. The as-fabricated Si-dominant anodes are eco-friendly as theyare made using aqueous solutions, thus avoiding toxic solvents. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich may be undesirable, for the reasons discussed above.

FIG. 15. Capacity retention (FIG. 15A) and Normalized capacity retention(FIG. 15B) curves of: (dotted line) the standard Si anode//NCA cathodefull cells—Control; and (solid line) the as-fabricated Si anode//NCAcathode full cells. The standard Si anodes contain about 80 wt % Si, 5wt % graphite and 15 wt % glass carbon (from resin), and may belaminated on 15 μm Cu foil. The average loading may be about 2-5 mg/cm².The as-fabricated Si anodes may be prepared by mixing Si powders, 20 wt% PMVMA & Tannic Acid (2/1 wt %) aqueous solution, and 5 wt % Super P,then coating the as-prepared Si slurry on the surface of 20 μm Cu foilfollowed by annealing at 550° C. for 1 hour. The final Si anodes containabout 90 wt % Si, 5 wt % Super P, and 5 wt % pyrolyzed carbon (fromPMVMA & Tannic Acid (2/1 wt %) binders). The average loading may beabout 2-6 mg/cm². The cathodes contain about 92 wt % NCA, 4 wt %conductive carbon and 4 wt % PVDF, and may be coated on 15 μm Al foil.The average loading may be about 20-30 mg/cm². The electrolytes used maybe 1.2M LiPF₆ in FEC/EMC (3/7 wt %).

The long-term cycling program for these cells may be the same as shownin FIG. 8.

FIG. 15 shows that the as-fabricated Si-dominant anode-based Li-ion fullcells using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders as disclosed have similar capacityand capacity retention with the control. As discussed above, the Sianodes using water-soluble maleic anhydride- and/or maleicacid-containing polymers as binders (with or without further additives)as disclosed herein are relatively inexpensive and are straightforwardto make. The as-fabricated Si-dominant anodes are eco-friendly as theyare made using aqueous solutions, thus avoiding toxic solvents. ControlSi-dominant anodes having about 80-85 wt % Si were manufactured with anNMP-containing organic solvent using a standard manufacturing processwhich may be undesirable, for the reasons discussed above.

Thus, as disclosed herein, using water-soluble maleic anhydride- and/ormaleic acid-containing polymers/co-polymers, derivatives, and/orcombinations (with or without additives) as binders for Si-dominantanodes may have the following one or more advantages: (i)Environmentally friendly; (2) Low cost; (3) Easier and/or fasterprocessing; (4) Improved manufacturing ability; (5) Better quality; (6)Flexibility of formulation design; and/or (7) Satisfactory carbon yieldafter pyrolysis.

As utilized herein, “and/or” means any one or more of the items in thelist joined by “and/or”. As an example, “x and/or y” means any elementof the three-element set {(x), (y), (x, y)}. In other words, “x and/ory” means “one or both of x and y”. As another example, “x, y, and/or z”means any element of the seven-element set {(x), (y), (z), (x, y), (x,z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one ormore of x, y and z”. As utilized herein, the term “Example” meansserving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “e.g.,” and “for example” set off lists ofone or more non-limiting examples, instances, or illustrations. Asutilized herein, a battery, circuitry or a device is “operable” toperform a function whenever the battery, circuitry or device comprisesthe necessary hardware and code (if any is necessary) or other elementsto perform the function, regardless of whether performance of thefunction is disabled or not enabled (e.g., by a user-configurablesetting, factory trim, configuration, etc.).

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

The invention claimed is:
 1. A battery electrode, the electrodecomprising an electrode coating layer comprising from about 1 wt % to 95wt % Si; wherein said electrode coating layer further comprises awater-soluble maleic anhydride- or maleic acid-containing polymerbinder; and wherein said polymer binder comprises Poly(methyl vinylether-alt-maleic anhydride); Poly(methyl vinyl ether-alt-maleic acid);Poly(styrene-alt-maleic acid) sodium salts; Poly(styrene-co-maleicacid), partial isobutyl esters; Poly(styrene-co-maleic acid), partialisobutyl/methyl mixed esters; Poly(styrene-alt-maleic anhydride),partial methyl esters; Poly(isobutylene-alt-maleic anhydride);Poly(maleic anhydride-alt-1-octadecene); Poly(ethylene-alt-maleicanhydride); Polyethylene-graft-maleic anhydride;Polypropylene-graft-maleic anhydride; Polyisoprene-graft-maleicanhydride; orPolystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleicanhydride; and wherein said polymer binder further comprises afunctional compound additive, wherein said functional compound additivecomprises cyclodextrin-based compounds or tannic acid.
 2. The electrodeaccording to claim 1, wherein said polymer binder comprises a lithiumsalt of a maleic anhydride- or maleic acid-containing polymer.
 3. Theelectrode according to claim 1, wherein said polymer binder furthercomprises a conductive additive, wherein said conductive additivecomprises Super P carbon black, graphite, graphene, carbon nanofibers,carbon fibers, carbon nanotubes, porous carbons and/or other types ofzero-, one-, two-, or three-dimensional carbon materials.
 4. Theelectrode according to claim 1, wherein the electrode coating layercomprises more than 70% silicon.
 5. The electrode according to claim 1,wherein the battery electrode is in a lithium ion battery.
 6. Theelectrode according to claim 1, wherein the electrode coating layer ispyrolyzed.
 7. A method of forming a battery electrode, the methodcomprising: creating an electrode coating layer from an electrode slurrycomprising an aqueous solution of a maleic anhydride- or maleicacid-containing polymer binder and about 1 wt % to 95 wt % Si powder,with optional additives; fabricating a battery electrode by coating theslurry on a current collector; and pyrolyzing said electrode coatinglayer; wherein said polymer binder comprises Poly(methyl vinylether-alt-maleic anhydride); Poly(methyl vinyl ether-alt-maleic acid);Poly(styrene-alt-maleic acid) sodium salts; Poly(styrene-co-maleicacid), partial isobutyl esters; Poly(styrene-co-maleic acid), partialisobutyl/methyl mixed esters; Poly(styrene-alt-maleic anhydride),partial methyl esters; Poly(isobutylene-alt-maleic anhydride);Poly(maleic anhydride-alt-1-octadecene); Poly(ethylene-alt-maleicanhydride); Polyethylene-graft-maleic anhydride;Polypropylene-graft-maleic anhydride; Polyisoprene-graft-maleicanhydride; orPolystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleicanhydride; and wherein said polymer binder further comprises afunctional compound additive, wherein said functional compound additivecomprises cyclodextrin-based compounds or tannic acid.
 8. The methodaccording to claim 7, wherein said polymer binder comprises a lithiumsalt of a maleic anhydride- or maleic acid-containing polymer.
 9. Themethod according to claim 7, wherein said polymer binder furthercomprises a conductive additive, wherein said conductive additivecomprises Super P carbon black, graphite, graphene, carbon nanofibers,carbon fibers, carbon nanotubes, porous carbons and/or other types ofzero-, one-, two-, or three-dimensional carbon materials.
 10. The methodaccording to claim 7, wherein the electrode coating layer comprises morethan 70% silicon.
 11. The method according to claim 7, wherein thebattery electrode is in a lithium ion battery.